U.S. Pat. Des. 350,684, issued to R. A. Campfield disclosed a windshield repair tool used to hold and position a resin injection head along the length of a crack in a windshield. One problem with this tool is that lateral stability with a single large suction cup mandated the use of two laterally spaced pressure adjustment bolts on one end of the frame in order to maintain the opposite end holding the injection head generally perpendicular to the windshield. In this tool the suction cup may be conveniently held beneath the palm of one's hand and moved along the crack. It is convenient to follow a sharply turning crack. Another problem with this single suction cup tool is it is not possible to maintain sufficient downward pressure to inject resin into the tightly closed portion of a crack. However, it is inconvenient to equally adjust two bolts over varying slopes as the tool is moved along the crack in the windshield.
U.S. Pat. No. 5,589,018 disclosed a repair tool utilizing two perpendicularly disclosed arms. One of the arms has suction cups on opposite end portions. The other arm is adapted to hold an injection head on one end and a single pressure adjustment bolt on the other opposite end portion. Utilization of two suction cups provided sufficient lateral stability to enable pressure to be conveniently adjusted with a single bolt thereby simplifying use. One problem with this design however, was longitudinal instability. Another problem is that the large separation between the cups, and the close proximity of the injection head to the cups usually mandates that in use one straddle the crack being repaired. It is not possible to follow a crack which turns toward the tool when the widely separated suction cups are adjacent to the crack on the same side of the crack. If a suction cup is moved over the crack suction is lost. Loss of suction in one of the two cups when moving over a crack or chip could cause the injection head to separate from the crack. What is worse is that if the suction cup lubricant penetrates the crack, then it is not possible for the resin to properly bond in the crack.
Additionally, widely separated suction cups mandates a greater distance between those cups and the injection head. This greater distance is required to follow a bending crack in a windshield without passing the suction cup over the crack. A greater distance between the injection head and the suction cups means less leverage and a smaller possible downward force on the injection head. This greater distance also mandates greater downward pressure exerted by the adjusting bolt to maintain comparable downward pressure on the crack by the injection head. If this tool is used with its suction cups straddling the crack then the force exerted by the single bolt is exerted on the injected crack causing it to separate. This separation causes air pockets to form in the crack resulting in an unsatisfactory bond.
On a typical crack which runs along closely beside the edge of a windshield before terminating at the edge, the inventor has found that it was advantageous to use the single cup tool on the portion of the crack at the edge of the window, and that it was advantageous to use the dual suction cup tool on the portion of the crack terminating in the central portion of the windshield. On the portion of the crack terminating in the central portion of the windshield it was advantageous to use the dual suction cup tool because with the dual suction cup tool more pressure could be exerted on the injection head. This greater pressure was needed in order to inject the tightly closed portion of the crack. On the portion of the crack terminating at the edge of the windshield, the dual suction cup tool could not typically be used either because there was insufficient room between the windshield edge and the crack to position the crack between the dual suction cups; or alternatively, the crack turned too sharply for use of this tool. What is needed is a better tool, one which can exert greater injection head pressure, follow a sharply turning crack, and seat wholly on a single side of the crack so that it could follow the crack all the way to the edge of the windshield.